This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our studies of metabolism, of high density lipoproteins (HDL) offer unique insights into lipid metabolism and transport that will be of value in understanding atherosclerosis at a molecular level. Methods developed in our laboratory have allowed us to document previously unreported molecular subspecies of HDL, each of which may play a specific antiatherogenic role associated with HDL. HDL subspecies purified from plasmas of normo- and dyslipidemic subjects reveal a variety of proteins. To date we have identified over seventy candidate proteins that associate with discrete HDL particles, several not previously recognized in the human proteome. Mass spectroscopic identification is of most benefit for the identification of proteins for which we have no specific antibodies, for proteins of low concentration, and for proteins which are not generally considered to associate with HDL. Our understanding of the HDL protein components consisting of lipid transfer factors such as cholesterol transfer protein, lecithin:cholesterol transferase, phosholipid transfer protein, hepatic lipase, plasma protease inhibitors, apoE, apoAIV, and apoL is paramount to our ability to understand the metabolic function of HDL-mediated protection in coronary artery disease. We are using mass spectrometry to study the molecular speciation of HDL in nine previously unrecognized monogenic disorders of HDL metabolism which we have identified by deep sequencing of mutations in extreme lipoprotein phenotypes.